1. Field of the Invention
The invention relates to pump jacks for traveling up and down scaffolding poles, and is directed more particularly to a handle assembly which prevents accidental sliding of the pump jack down a pole.
2. Description of the Prior Art
It is known to use pump jacks in scaffolding systems for raising and lowing scaffolding platforms. Typically, a number of pump jack poles are secured in spaced relationship to a building or other edifice to be worked on, and pump jacks are utilized to carry the scaffolding platforms up and down the poles. Scaffolding staging or platforms are extended across support arms provided on the pump jacks. Workers stand on the scaffolding platforms and operate the pump jacks to move the platforms up and down along the pump jack poles.
Each pump jack typically includes a frame with an upper and a lower shackle. A pump arm is pivotally connected to the frame to operate the two shackles alternately. The operation causes the upper shackle to grip the pole permitting the frame to step upward along the pole. Thereafter, the lower shackle grips the pole and the upper shackle steps up to a next position on the pole. In this manner, one of the shackles steps up the pole while the other shackle grips the pole. Pump jacks are shown and described in U.S. Pat. No. 4,597,471, issued Jul. 1, 1986 and U.S. Pat. No. 4,955,584 issued Sep. 11, 1990.
The upper shackle includes a rod which can be applied engaged with the pole to grip the pole. A crank handle coupled to the rod permits winding and unwinding of the rod. To lower the pump jack, a release lever releases the lower shackle from engagement with the pole. The crank handle is then operated to unwind the rod, thereby rolling the pump jack down the pole. In order to prevent accidental unwinding of the crank handle, the handle may be provided with a safety locking position in which the handle is disposed inwardly of the pump jack frame so as to be retained in place by the pump jack frame, which blocks the handle to prevent accidental unwinding of the rod. A pump jack of the aforedescribed construction has been disclosed in U.S. Pat. No. 4,463,824, issued Aug. 7, 1984, and U.S. Pat. No. 4,942,941 issued Jul. 4, 1990.
One of the most critical concerns when using pump jacks is the safety of the workers standing on the staging supported by the pump jacks. Despite the presence of safety locking handles, which should be positioned inwardly to prevent accidental unwinding, accidental slipping of the pump jack down the pole has occurred when workers have forgotten to move the handle into the safety position. In U.S. Pat. No. 4,463,824, there is provided a crank handle assembly wherein the handle is movable to a safety locking position in which the handle is held in place by the pump jack pole and thereby prevents accidental unwinding of the rod, and thereby avoids the pump jack accidentally slipping down the pole. The handle is positionable in either of two positions. In a first position, an arm connected to the rod extends downwardly and a handle portion connected to the arm extends inwardly in position to engage the front surface of the pole, to prevent unwinding of the rod. In a second position, the arm extends upwardly and the handle extends outwardly in a cranking position. Thus, to change the handle assembly from the safety (first) position, to the crank (second) position it is necessary that the handle be grasped while locked against the pole, pulled outwardly and then upwardly. To change the handle back to the safety position, the handle must be pulled outwardly, downwardly and inwardly and up against the pole surface. It is deemed beneficial to have available a handle assembly which is more easily and simply movable between safety and crank positions.
In U.S. Pat. No. 4,942,941 there is provided a handle assembly having a safety and crank feature substantially as taught by the '824 patent, and, in addition, is provided with an anti-spin feature at the end of the rod opposite from the handle assembly end. The anti-spin feature comprises a rubber disc which can be pressed against an end of the rod by tightening down on an external bolt. While the rubber disc exercises some restraint on rotation of the rod, it is desirable to have a more positive locking means which would operate to stop rotation of the rod, as opposed to merely slowing or damping rotation. It is further desirable to have a locking means which is operative without the necessity of tightening a bolt, an exercise which could be problematic in an emergency situation.
3. Summary of the Invention
An object of the invention is, therefore, to provide a novel pump jack handle assembly having a safety position in which turning of the handle assembly is blocked by a frame portion of the pump jack.
A further object of the invention is to provide such a novel handle assembly which is spring-biased toward a safety position.
A still further object of the invention is to provide such a handle assembly as may be moved through a short distance in one direction to reach a crank position and which, upon release is adapted to snap back to a safety position.
A still further object of the invention is to provide such a handle assembly having a second safety feature, operable in the aforementioned safety position, which interlocks the rod with a rod mounting to prevent rotation of the rod in the mounting.
Another object is to provide a pump jack with a novel handle assembly for rotating a pole-gripping rod of a shackle assembly, said handle assembly having a locking member that is movable by the handle assembly into interlocking engagement with a portion of the jack, whereby the handle assembly is prevented from rotating said pole-gripping rod.
With the above and other objects in view, as will herewith appear, a feature of the present invention is the provision of a handle assembly for a pump jack having a shackle including a yoke with opposed side plates rotatably mounting a rod spanning the side plates and engageable with a pump jack pole and for rolling along a surface of the pole during descent of the pump jack along the pole. The handle assembly comprises an extension of the rod extending outwardly from one of the side plates, a free end of the rod extension being spaced from the one side plate. A coil spring is disposed around the rod extension. A sleeve is disposed around the rod extension and around the coil spring, a first end of the sleeve being opposed to the one side plate and a second end of the sleeve facing outwardly from the one side plate. A bar is fixed to the sleeve and extends lengthwise thereof with a free end extending beyond the second end of the sleeve. An arm extends transversely of the rod extension, the rod extension free end being pivotally connected to the arm at a first location proximate a first end of the arm, and the bar free end being pivotally connected to the arm at a second location proximate the first end of the arm and spaced from the first location in a direction toward a free end of the arm. The coil spring urges the arm first end outwardly from the yoke, causing the bar to move inwardly toward the yoke, to urge the sleeve first end toward the yoke. A projection extends outwardly from the one side plate and is engageable by the sleeve first end, the projection and the sleeve first end being configured such that the engagement of the sleeve first end and the projection serves to interlock the sleeve and the projection such that the sleeve is prevented from rotating, and the handle is prevented from rotating, and thereby the rod, such that the rod is fixed and unable to roll along the surface of the pole.
In accordance with a further feature of the invention, there is provided a handle assembly for a pump jack having a shackle including a yoke with opposed side plates rotatably mounting a rod spanning the side plates and engageable with a pump jack pole and for rolling along a surface of the pole during descent of the pump jack along the pole. The handle assembly comprises an extension of the rod extending outwardly from one of the side plates, a free end of the rod extension being spaced from the one side plate. A coil spring is disposed around the rod extension. A sleeve is disposed around the rod extension and around the coil spring, a first end of the sleeve being opposed to the one side plate and a second end of the sleeve facing outwardly from the one side plate. A bar is fixed to the sleeve and extends lengthwise thereof with a free end extending beyond the second end of the sleeve. An arm extends transversely of the rod extension, the rod extension free end being pivotally connected to the arm at a first location proximate a first end of the arm, and the bar free end is pivotally connected to the arm at a second location proximate the first end the arm and spaced from the first location in a direction toward a free end of the arm, and a handle is mounted on the free end of the arm. A spring is operative to pivot the arm about the first and second locations to urge the arm free end, and thereby the handle, in a direction toward the yoke and aligned with a frame member supporting the shackle and which blocks rotational movement of the arm and the handle, and thereby the rod, to further prevent the rod from rolling along the surface of the pole.
In accordance with a still further feature of the invention, there is provided a handle assembly for a pump jack having a shackle including a yoke with opposed side plates rotatably mounting a rod spanning the side plates and engageable with a pump jack pole for rolling along a surface of the pole during descent of the pump jack along the pole. The handle assembly comprises an extension of the rod extending outwardly from one of the side plates, a free end of the rod extension being spaced from the one side plate. A coil spring is disposed around the rod extension. A sleeve is disposed around the rod extension and around the coil spring, a first end of the sleeve being opposed to the one side plate and a second end of the sleeve facing outwardly from the one side plate. A bar is fixed to the sleeve and extends lengthwise thereof with a free end extending beyond the second end of the sleeve. An arm extends transversely of the rod extension, the rod extension free end being pivotally connected to the arm at a first location proximate a first end of the arm, and the bar free end being pivotally connected to the arm at a second location proximate the first end of the arm and spaced from the first location in a direction toward a free end of the arm. A handle is mounted on the free end of the arm.
The coil spring urges the arm first end outwardly from the yoke, causing the bar to move inwardly toward the yoke, to urge the sleeve first end toward the yoke. A projection extends outwardly from the one side plate and is engageable by the sleeve first end, the projection and the sleeve first end being configured such that the engagement of the sleeve first end and the projection serves to interlock the sleeve and the projection such that the sleeve is prevented from rotating, and the handle is prevented from rotating, and thereby the rod, such that the rod is fixed and unable to roll along the surface of the pole. The spring is operative to pivot the arm about the first and second locations to urge the arm free end and thereby the handle in a direction toward the yoke and aligned with a frame member supporting the shackle and which blocks rotational movement of the arm and the handle, and thereby the rod, to further prevent the rod from rolling along the surface of the pole.
The above and other features of the invention, including various novel details of construction and combinations of parts, will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular device embodying the invention is shown by way of illustration only and not as a limitation of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention.